Flocculation and settling of inorganic particles in a salt solution

ABSTRACT

Predominantly inorganic water-insoluble particles suspended in aqueous salt solutions are flocculated and settled by adding to the solution a water-soluble copolymer of acrylamide and an alkali metal salt of vinyl sulfonic acid. Preferred copolymer is acrylamide- sodium vinyl sulfonate.

United States Patent Inventor Daniel J. Monagle Wilmington, Del.

Appl. No. 873,672

Filed Nov. 3, 1969 Patented Nov. 2, 1971 Assignee Hercules Incorporated Wilmington, Del.

rLoccuLA'noN Aivn sEr'ruNo 0F INORGANIC PARTICLES IN A SALT soumon Primary Examiner-Reuben Friedman Assistant Examiner-Thomas G. Wyse Attorney-Lewis H. Wilson ABSTRACT: Predominantly inorganic water-insoluble particles suspended in aqueous salt solutions are flocculated and settled by adding to the solution a water-soluble copolymer of acrylamide and an alkali metal salt of vinyl sulfonic acid. Preferred copolymer is aerylamide--sodium vinyl sulfonate.

FLOCCULATION AND SETTLING OF INORGANIC PARTICLES IN A SALT SOLUTION This invention relates to the separation of predominantly inorganic water-soluble suspended particles from aqueous salt solutions. In particular, it relates to such separation with certain water-soluble anionic polyelectrolyte preferably of high molecular weight. In a more specific embodiment, it relates to the separation of suspended particles from aqueous salt solutions employed in the treatment of water-soluble ores.

Water-soluble polyelectrolyte polymers based on acrylamide and/or acrylic acid are widely known and used for separating predominantly inorganic suspended particles from aqueous media. Most of these polyelectrolyte polymers, however, lose a significant amount of their effectiveness when used in the presence of salt solutions.

One area where this loss of effectiveness is a serious problem is in the refinement of water-soluble ores. Such ores, as mined, generally contain a significant amount of insoluble clay. This clay is removed by agitating the ore in a saturated. salt solution and then decanting (desliming) the resultant clay suspension. The decanted liquid normally contains up to about Spercent suspended clay solids which is allowed to settle out and the salt solution is returned to the system for reuse. To reduce the time required for such settling, a flocculant is In accordance with this invention, it has been found that a copolymer comprised of a major portion of acrylamide and a minor portion of an alkali metal or ammonium salt of vinyl sulfonic acid is an effective fiocculant and settling aid for the separation of predominantly inorganic water-insolublesuspended particles from aqueous salt solutions. Specifically, copolymers containing about 85 to 98 percent by weight, and preferably 90 to 97 percent by weight of acrylamide and to 2 percent by weight and preferably 10 to 3 percent by weight of the alkali metal salt of vinyl sulfonic acid having a reduced specific viscosity (RSV) of at least about 9, preferably at least about 12, have been found to promote rapid flocculation and settling of such suspended solid materials. The copolymer is: preferably used in the amount of at least about 0.01 lb./ton of; suspended material in the salt solution.

The preferred salt of vinyl sulfonic acid is the sodium salt. However, the potassium, lithium and ammonium salts are also usefuL I 7 M In the following examples, where parts and percentages arev by weight unless otherwise indicated, the invention is illustrated in several of its embodiments. The RSV referred to in the examples is measured on a 0.1 percent solution of the copolymer in a 0.2 molar aqueous Na,SO solution at 25 C.

EXAMILE POTASI-I ORE A sample of sylvinite potash ore from the Carlsbad district of New Mexico was scrubbed in the conventional manner in the presence of a saturated KCl solution. Solids content of the ore-brine mixture was about 50 percent by weight. This was screened on a 30-mesh screen, to remove fines. The filtered brine contained about 1 percent by weight clay particles suspended therein.

Specimens of the brine-clay suspension were treated with varying amounts of a copolymer containing 95.5 percent acrylamide and 4.5 percent sodium vinyl sulfonate (SVS), having an RSV of 16.4. The specified amount of copolymer was added to a filtrate in a graduated 100 ml. cylinder and the mass was thoroughly agitated to assure complete mixing of clay and copolymer. The volume of supernatant liquid was noted at several time intervals and compared with a control containing no flocculant and with a commercially available poly(acrylamide) flocculant sold for this use under the trade name BENEFITE M-l l. Results are recorded in table 1.

polymers,

Volume of supernatant (1111.) at (min.) Cone. (lbs./

ton/clay) 1 2 3 5 Flocculant Benefite M-11 EXAMPLE 2 BORAX ORE Separation of clay from a borax ore solution was demonstrated by combining 579 parts of borax ore (70.23 percent sodium borate decahydrate, 3.83 percent I-I,O and 25.94 per cent insoluble clay), 945 parts of sodium borate decahydrate and 1476 parts water at about C. to form a solution containing about 5 percent suspended clay.

A copolymer of 4.5 percent SVS and 95.5 percent acrylamide (RSV 16.4) was mixed with several cc. portions of the solution in graduated cylinders and the volume of supernatant liquid was measured at several time intervals. The test specimens were maintained at about 95 C. during testing. Test results are recorded in table 2 along with results where no flocculant was used and results using a commercially available acrylamide-based anionic flocculant sold for this use under the trade name SEPARAN MGL.

TABLE 2 Volume 0! super (ml.) at (mln.)---

Lbs./ton 2 4 Floeeulant Example 2 EXAMPLE 3 yolume (mil) in Cone. (lbs./

Flocculant ton/clay) 0.

Control (none) EXAMPLES 4 TO 1 1 To demonstrate the flocculating ability of the copolymers of this invention, a series of 5 percent dispersions of kaolin clay in salt solutions were prepared. To each of these there were added various concentrations of the 95.5/4.5 acrylamide-SVS copolymer of RSV 16.4. The flocculation rates of these mixtures are recorded in the following tables.

' TABLE 4 Supernatant volume (ml.) at Flocculant (min.)- cone. (lbs./ Ex. No. Salt solution ton) 0.5 1 2 3 4 5 3 1 2% 4% 4 6 6 55 0 64 4 5% Sdmm mate 0. 4 22 42 56 63 67 70 0.8 30 52 65 70 72 73 TABLE 5 Supernatant volume (ml.) at Flocculant min. cone. (lbs./ Ex. No. Salt solution ton) 0. 5 1 2 3 4 5 o 3 2 1% 4% 53 55 62 5 2% calcium chloride .V 4 9 27 49 57 62 61 0. 8 19 40 57 64 68 71 TABLE 6 Y Supernatant volume (ml.) at Flocculant (min.) cone. (lbs./ Ex. No. Salt solution ton) 0.5 1 2 3 4 5 0 0 40 1 1 2 6 5% sodium acetate 8:: g g; 2g 07 8 26 50 62 67 69 71 TABLE 7 Supernatant volume (ml.) at Flocculant (min.)- cone. (lbs./ Ex. No. Salt solution ton) 0. 5 1 3 4 5 0 0 0 1 1 2 3 0. 1 6 16 40 52 60 64 7 2% sodium carbonate 0.2 29 53 70 74 76 78 0. 4 67 74 78 80 82 82 0. 8 80 82 85 85 85 85 TABLE 8 Supernatant volume (ml.) at Flocculant (min.) cone. (lbs./ Ex. No. Salt solution ton) 0.5 1 2 3 4 5 0 0 0 1 1 3 4 8 5% disodium acid 0. 1 3 34 48 54 58 phosphate. 0. 2 11 35 53 60 64 67 0. 4 53 67 73 75 77 79 TABLE 9 Supernatant volume (ml.) at Flocculant (min.) cone. (1bs./ Ex. No. Salt solution ton) 0.5 1 2 3 4 5 0 0 0 1 2 4 8 0. 1 4 6 16 27 36 44 9 1% sodium sulfate 0. 2 8 41 53 60 63 0. 4 15 31 53 61 66 68 0.8 55 74 76 77 7 79 TABLE 10 Supernatant volume (ml.) at Flocculant (min.) cone. (lbs./ Ex. No. Salt solution ton) 0. 5 1 2 3 4 5 0 0 1 2 6 0. 1 3 6 9 15 19 23 10 2% sodium sulfate 0. 2 9 22 42 56 62 66 0. 4 22 46 62 70 72 70 0. 8 60 69 75 78 79 85 TABLE 11 Supernatant volume (ml.) at Flocculant min.)- cono. (lbsJ Ex. No. Salt solution ton) 0.5 1 2 3 4 5 g g 1% 22 a? 43 0. 11 10% sodium sulfate o. 4 2 n 49 58 0. 8 20 42 69 71 EXAMPLE 12 A 50 percent aqueous slurry of uranium ore containing about 0.07% U 0 was ball milled and leached for 44 hours with sulfuric acid at a pH of 1.5. The resulting uranium sulfate solution was diluted with water to reduce the insolubles content to percent. This material was treated with the 95.5 /4.5 copolymer and the settling rates are recorded in table 12.

A 50 percent aqueous slurry of copper ore containing about 2.2 percent copper silicate was ball milled and leached with sulfuric acid at a pH of 1.6 for 2 hours. The resulting copper sulfate solution was diluted with water to reduce the solids content to percent. This material was treated with various amounts of the 95.5/4.5 copolymer and the settling rates are recorded in table 13.

TABLE 13 Flocculant Supernatant volume (ml.) at (mln.) cone. (1bs./ Ex. No. ton) 0. 5 1 2 3 4 5 The alkali metal vinyl sulfonate-acrylamide copolymer employed in this invention must have a relatively high molecular weight in order to realize the best performance. Viscosity measurement is the only really practical and meaningful way known for measuring the molecular weight of copolymers having the high molecular weights of those employed in this invention, and this method is widely used and accepted. Thus the useful copolymers according to this invention are those having an RSV of at least about 9 measured on a 0.1 percent solution of the copolymer in a 0.2 molar aqueous Na SQ, solution at 25 C. Preferably, the RSV will be at least about 12. Copolymers useful in the process of this invention can be prepared by known methods, e.g., by the methods taught in US. Pat. Nos. 3,336,269 or 3,336,270.

What I claim and desire to protect by Letters Patent is:

l. A process for flocculating and settling predominantly inorganic water-insoluble suspended particles from an aqueous salt solution which comprises adding to said salt solution a water-soluble copolymer consisting essentially of acrylamide and an alkali metal or ammonium salt of vinyl sulfonic acid.

2. The process of claim 1 where the vinyl sulfonic acid salt is sodium vinyl sulfonate.

3. A process for separating suspended insoluble inorganic particles from an aqueous salt solution which comprises adding to said salt solution per ton of suspended particles at least about 0.01 lb. of a water-soluble copolymer consisting essentially of about 85 to 98 percent acrylamide by weight and about 15 to 2 percent by weight of a salt of vinyl sulfonic acid selected from the class consisting of alkali metal and ammonium salts, said copolymer having an RSV of at least about 9 rneasureclm 0.1 percent solution in 0.2 M sodium sulfate at 25 C.

4. The process of claim 3 where the vinyl sulfonic acid salt is sodium vinyl sulfonate.

l i t l l 

2. The process of claim 1 where the vinyl sulfonic acid salt is sodium vinyl sulfonate.
 3. A process for separating suspended insoluble inorganic particles from an aqueous salt solution which comprises adding to said salt solution per ton of suspended particles at least about 0.01 lb. of a water-soluble copolymer consisting essentially of about 85 to 98 percent acrylamide by weight and about 15 to 2 percent by weight of a salt of vinyl sulfonic acid selected from the class consisting of alkali metal and ammonium salts, said copolymer having an RSV of at least about 9 measured in a 0.1 percent solution in 0.2 M sodium sulfate at 25* C.
 4. The process of claim 3 where the vinyl sulfonic acid salt is sodium vinyl sulfonate. 